Helmet



FIG. 1 is a perspective view of a helmet;

FIG. 2 is a front view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a right-side view thereof;

FIG. 5 is a left-side view thereof;

FIG. 6 is a rear view thereof; and,

FIG. 7 is a bottom view thereof with the unclaimed strap portions omitted.

The broken lines, including the straps in broken lines, depict environmental subject matter only and form no part of the claimed design. 

CLAIM The ornamental design for a helmet, as shown and described. 